Abstract
BackgroundLittle information is available on the effect of allergen-specific immunotherapy on airway responsiveness and markers in exhaled air. The aims of this study were to assess the safety of immunotherapy with purified natural Alt a1 and its effect on airway responsiveness to direct and indirect bronchoconstrictor agents and markers in exhaled air.MethodsThis was a randomized double-blind trial. Subjects with allergic rhinitis with or without mild/moderate asthma sensitized to A alternata and who also had a positive skin prick test to Alt a1 were randomized to treatment with placebo (n = 18) or purified natural Alt a1 (n = 22) subcutaneously for 12 months. Bronchial responsiveness to adenosine 5'-monophosphate (AMP) and methacholine, exhaled nitric oxide (ENO), exhaled breath condensate (EBC) pH, and serum Alt a1-specific IgG4 antibodies were measured at baseline and after 6 and 12 months of treatment. Local and systemic adverse events were also registered.ResultsThe mean (95% CI) allergen-specific IgG4 value for the active treatment group increased from 0.07 μg/mL (0.03-0.11) at baseline to 1.21 μg/mL (0.69-1.73, P < 0.001) at 6 months and to 1.62 μg/mL (1.02-2.22, P < 0.001) at 12 months of treatment. In the placebo group, IgG4 value increased nonsignificantly from 0.09 μg/mL (0.06-0.12) at baseline to 0.13 μg/mL (0.07-0.18) at 6 months and to 0.11 μg/mL (0.07-0.15) at 12 months of treatment. Changes in the active treatment group were significantly higher than in the placebo group both at 6 months (P < 0.001) and at 12 months of treatment (P < 0.0001). However, changes in AMP and methacholine responsiveness, ENO and EBC pH levels were not significantly different between treatment groups. The overall incidence of adverse events was comparable between the treatment groups.ConclusionAlthough allergen-specific immunotherapy with purified natural Alt a1 is well tolerated and induces an allergen-specific IgG4 response, treatment is not associated with changes in AMP or methacholine responsiveness or with significant improvements in markers of inflammation in exhaled air. These findings suggest dissociation between the immunotherapy-induced increase in IgG4 levels and its effect on airway responsiveness and inflammation.
Highlights
Little information is available on the effect of allergen-specific immunotherapy on airway responsiveness and markers in exhaled air
It has been suggested that the bronchial responsiveness to inhaled adenosine 5′-monophosphate (AMP) may reflect changes in airway inflammation induced by allergen exposure[5,6] or by allergen immunotherapy[7] with greater precision and sensitivity than the response to direct bronchoconstrictor agents
Fourth patients (SIT group) declined the previous acceptance for participation after 6 months of treatment for social problems not related to the treatment
Summary
Little information is available on the effect of allergen-specific immunotherapy on airway responsiveness and markers in exhaled air. The aims of this study were to assess the safety of immunotherapy with purified natural Alt a1 and its effect on airway responsiveness to direct and indirect bronchoconstrictor agents and markers in exhaled air. Increased concentrations of exhaled nitric oxide (ENO)[8,9] and acidification of exhaled breath condensate (EBC)[10,11] have been demonstrated in asthma Both ENO and EBC pH are correlated with the number of eosinophils in the lower respiratory tract [11,12]. These parameters have been proposed as markers of airway inflammation and disease severity in asthma[13,14]
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